// Voiculescu Rafaela 321CA

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct{
    unsigned int h; //inaltimea crengii pe care se afla gutuia
    unsigned int g; //greutatea gutuii
} gutuie;

int compara(void* a,void* b)
{
    unsigned int val_a,val_b,vala,valb;
    val_a=(*((gutuie *)a)).h;
    val_b=(*((gutuie *)b)).h;
    vala=(*((gutuie *)a)).g;
    valb=(*((gutuie *)b)).g;
    if(vala<valb)
        return 1;
    else
        if(vala>valb)
            return -1;
        else
        {
            if(val_a<val_b)
                return 1;
            else
                if(val_a>val_b)
                    return -1;
                else
                    return 0;
        }
}

int main()
{
    //deschidere fisier de intrare, respectiv fisier de iesire
    FILE *in,*out;
    in=fopen("gutui.in","r");
    out=fopen("gutui.out","w");

    //citim numarul de gutui, inaltimea maxima si cu cat se ridica crengile
    int N,H,U;
    fscanf(in,"%d%d%d",&N,&H,&U);
     unsigned int *ridicari,*nivele;
    gutuie *date;
    date=(gutuie*) calloc(N,sizeof(gutuie));

    int i,k;
    unsigned int nr_max_gutui;
    ridicari = (unsigned int *) calloc(N,sizeof (unsigned int));
     nivele = (unsigned int *) calloc(N,sizeof (unsigned int));


    //citim datele despre fiecare creanga
    for(i=0;i<N;i++)
        fscanf(in,"%u%u",&date[i].h,&date[i].g);

    qsort(date,N,sizeof(gutuie),(__compar_fn_t)&compara);

    //for(i=0;i<N;i++)
      //  printf("%u %u\n",date[i].h,date[i].g);
    unsigned int minim=date[0].h;
    for(i=1;i<N;i++)
        if(date[i].h<minim)
            minim=date[i].h;

    //printf("%u\n",minim);
    if ((H-minim)%U!=0)
    nr_max_gutui=(H-minim)/U + 1;  //cate gutui ar putea fi maxim culese a.i. sa se respecte conditiile
    else
    nr_max_gutui=(H-minim)/U;
    //printf("%u\n",nr_max_gutui);

    int culese=0;
    unsigned int suma=0;
    for (i=0;i<N;i++)
       ridicari[i]=(H-date[i].h)/U +1;
    
    if (nr_max_gutui==N)
    	for (i=0;i<N;i++)
		suma=suma+date[i].g;
   else
    for(i=0;i<N;i++) 
        if(culese<nr_max_gutui)
            if(ridicari[i]>0&&nivele[ridicari[i]]!=ridicari[i])   //poate fi culeasa in conditiile date
            {
                suma+=date[i].g;
                culese++;
                nivele[ridicari[i]]++;
            }
        fprintf(out,"%u\n",suma);

    free(date);
    fclose(in);
    fclose(out);
    return 0;
}